Based on our vast experience with EASA PART 66 examination questions and question databanks, we have prepared a practice example of questions with explanations to practice for your next exam.
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Module 4: Electronic Fundamentals
- A semiconductor material doped with an element that has 5 valence electrons is known as what type?
- A. A C-type material
- B. An N-type material
- C. A P-type material
Correct Answer: B. An N-type material
Explanation: When an intrinsic semiconductor is doped with an element having 5 valence electrons (a pentavalent impurity), it donates extra free electrons. This creates an N-type (Negative-type) material where electrons are the majority charge carriers.
- What is the primary operational characteristic of a thyristor?
- A. High power handling
- B. High voltage handling
- C. High current handling
Correct Answer: A. High power handling
Explanation: A thyristor, like an SCR, is a semiconductor device designed to act as a switch in high-power applications. Its key feature is its ability to control and switch large amounts of both current and voltage, resulting in high power handling capability.
- What is the approximate forward voltage drop across a standard Light Emitting Diode (LED)?
- A. 0.2V
- B. 1.6V
- C. 0.4V
Correct Answer: B. 1.6V
Explanation: The forward voltage drop of an LED is significantly higher than a standard silicon diode. It varies with the color of the light, but a typical value is around 1.6 to 2.2 volts.
- Which type of diode is specifically designed to emit photons when forward biased?
- A. An LED
- B. A Schottky diode
- C. A Gunn diode
Correct Answer: A. An LED
Explanation: An LED (Light Emitting Diode) is a specialized PN-junction diode that, when forward biased, allows electrons and holes to recombine and release energy in the form of light photons.
- A diode has its anode connected to +4V and its cathode to +2V. What is its status?
- A. Forward biased and conducting
- B. Reverse biased and not conducting
- C. Forward biased but not conducting
Correct Answer: A. Forward biased and conducting
Explanation: For a diode to be forward biased and conduct, its anode must be more positive than its cathode. Since +4V is more positive than +2V, the diode is forward biased and will conduct current.
- In a semiconductor diode, the direction of electron flow is from where to where?
- A. From Cathode to Base
- B. From Cathode to Anode
- C. From Anode to Cathode
Correct Answer: B. From Cathode to Anode
Explanation: Electron flow is the movement of negative charges. In a diode, electrons flow from the negative terminal (N-type material, the Cathode) to the positive terminal (P-type material, the Anode).
- When a hole from the P-region of a semiconductor diffuses across the junction into the N-region, what does it become?
- A. A majority carrier in the N-region
- B. It lowers the potential barrier
- C. A minority carrier in the N-region
Correct Answer: C. A minority carrier in the N-region
Explanation: Holes are the majority carriers in P-type material. If a hole crosses the junction into the N-type material, where electrons are the majority carriers, the hole becomes a minority carrier.
- How does the forward bias voltage of a germanium diode compare to that of a silicon diode?
- A. It is lower than a silicon diode’s
- B. It is higher than a silicon diode’s
- C. It is the same as a silicon diode’s
Correct Answer: A. It is lower than a silicon diode’s
Explanation: A germanium diode has a lower energy band gap and therefore requires a lower forward voltage (approximately 0.3V) to begin conducting, compared to a silicon diode which requires approximately 0.7V.
- Once a thyristor (SCR) has been triggered ON, how is it typically switched OFF?
- A. By interrupting the main supply voltage
- B. By removing the gate voltage
- C. By applying a reverse bias to the gate
Correct Answer: A. By interrupting the main supply voltage
Explanation: Once an SCR is latched into its conducting state, the gate signal has no further control. To turn it off, the current flowing from anode to cathode must be reduced below a minimum ‘holding current’, which is usually achieved by removing the main supply.
- What is the resistance characteristic of a Silicon Controlled Rectifier (SCR) when it is in its ‘ON’ or conducting state?
- A. It has a very low resistance
- B. It has no change in resistance
- C. It has a very high resistance
Correct Answer: A. It has a very low resistance
Explanation: When an SCR is triggered ON, it acts like a closed switch. In this state, it presents a very low resistance path to the current flowing from its anode to its cathode.
- A piece of pure, undoped germanium at room temperature is considered to be what?
- A. It has an excess of electrons
- B. It has a deficit of electrons
- C. Electrically stable
Correct Answer: C. Electrically stable
Explanation: Pure semiconductor material, also known as intrinsic semiconductor, has a balanced crystal structure where the number of electrons is equal to the number of protons in the atoms, making it electrically neutral or stable.
- What are the charge carriers that constitute the majority of current flow in a forward-biased PN junction?
- A. Holes only
- B. Electrons and holes
- C. Electrons only
Correct Answer: B. Electrons and holes
Explanation: When a PN junction is forward biased, the potential barrier is lowered. This allows the majority carriers from both sides—holes from the P-region and electrons from the N-region—to flow across the junction, creating the main current.
- An amplifier is configured in a common base arrangement. What are its typical gain characteristics?
- A. Its voltage gain is high, but its current gain is slightly less than 1
- B. Both its voltage and current gain are high
- C. Its current gain is high, but its voltage gain is slightly less than 1
Correct Answer: A. Its voltage gain is high, but its current gain is slightly less than 1
Explanation: The common base configuration provides a high voltage gain and a very wide bandwidth, but its current gain (Alpha) is always slightly less than unity (1).
- Why is the common collector amplifier often referred to as an ’emitter follower’?
- A. Because the emitter current follows the collector current
- B. Because the emitter voltage closely follows the base voltage
- C. Because the emitter voltage follows the collector voltage
Correct Answer: B. Because the emitter voltage closely follows the base voltage
Explanation: In a common collector (emitter follower) circuit, the output is taken from the emitter. The emitter voltage is always one diode drop (approx 0.7V) less than the base voltage, so it ‘follows’ the input signal applied to the base.
- What are two primary classifications for electronic amplifiers based on their function?
- A. Common emitter or common collector amplifiers
- B. Voltage amplifiers or power amplifiers
- C. Voltage amplifiers or impedance amplifiers
Correct Answer: B. Voltage amplifiers or power amplifiers
Explanation: Amplifiers are often categorized by their primary purpose. A voltage amplifier is designed to increase the voltage level of a signal, while a power amplifier is designed to deliver a significant amount of power to a load.
- The ‘common base’ transistor configuration gets its name from what fact?
- A. The base is physically located between the emitter and the collector
- B. The base terminal is common to both the input and output circuits
- C. The base is made from n-type material
Correct Answer: B. The base terminal is common to both the input and output circuits
Explanation: In the common base configuration, the input signal is applied to the emitter, the output is taken from the collector, and the base is the common connection point for both the input and output signals.
- What is the cause of thermal runaway in a bipolar junction transistor?
- A. Excessive heat causing an uncontrolled increase in current flow
- B. Low heat causing minimum current flow
- C. Excessive heat causing a decrease in current flow
Correct Answer: A. Excessive heat causing an uncontrolled increase in current flow
Explanation: Thermal runaway is a positive feedback loop. As the transistor heats up, its internal leakage current increases. This increased current causes more heating, which in turn causes more leakage current, leading to a destructive, uncontrolled current flow.
- If you test a functional bipolar junction transistor between its emitter and collector terminals with an ohmmeter, what should you expect to read?
- A. A high resistance in one direction only
- B. A low resistance in both directions
- C. A high resistance in both directions
Correct Answer: C. A high resistance in both directions
Explanation: The path between the emitter and collector of a BJT consists of two diode junctions connected back-to-back (N-P-N or P-N-P). Therefore, an ohmmeter should show a very high resistance regardless of the polarity of the test leads.
- When a transistor is operating in its saturation region, it is acting like a closed switch. What is its resistance characteristic in this state?
- A. A very high resistance
- B. A very low resistance
- C. Zero resistance
Correct Answer: B. A very low resistance
**Explanation:** In the saturation region, the transistor is turned ‘fully on’. The voltage drop between the collector and emitter is at its minimum, and the transistor exhibits a very low resistance to current flow.
- For an audio system requiring the highest possible fidelity and linearity, which class of amplifier is most suitable?
- A. Class B
- B. Class C
- C. Class A
Correct Answer: C. Class A
Explanation: Class A amplifiers are the most linear and produce the least distortion (highest fidelity) because the amplifying device conducts current through the entire 360-degree cycle of the input signal.
